The present invention relates to a mechanism for positioning a biasing magnet in a magneto-optical disc drive.
A magneto-optical disc drive is provided with a biasing magnet for applying a biasing magnetic field to a magneto-optical disc when data is recorded on the magneto-optical disc.
Generally, the biasing magnet has an elongated shape, which is positioned in parallel with one surface of the magneto-optical disc with a predetermined clearance with respect to the disc surface. The elongating direction of the magnet is aligned to the radial direction of the disc.
In order to perform the data recording operation stably, it is important that the magnetic field applied to the magneto-optical disc should be maintained constant. For this purpose, it is important that the biasing magnet accurately positioned when the data recording operation is performed.
In a conventional device, the biasing magnet may not be located at its operative position accurately due to individual manufacturing errors of the mechanism. That is, the distance between the biasing magnet and the disc and/or the degree of parallelization with respect to the disc surface are affected by individual differences of the size of a member used for positioning the biasing magnet. If the magnet is not accurately position, the data recording operation cannot be performed reliably.
It is therefore an object of the invention to provide an improved mechanism for accurately positioning a biasing magnet in a magneto-optical disc drive.
For this purpose, according to an aspect of the invention, there is provided a biasing magnet positioning mechanism for a magneto-optical disc drive, which includes a cartridge holder that detachably holds a disc cartridge accommodating a magneto-optical disc, the disc cartridge being formed with an opening for exposing a part of a surface of the magneto-optical disc accommodated therein, a cartridge holder moving mechanism that moves the cartridge holder, within a chassis, between a cartridge insertion/withdrawal position at which the disc cartridge can be inserted in or withdrawn from the cartridge holder, and a loading position at which data recording/reproducing operation can be performed, a biasing magnet for applying a magnetic field to a magneto-optical disc, the biasing magnet being provided with a first contact portion on a side closer to a rotational axis of the magneto-optical disc and a second contact portion on a side farther from the rotational axis of the magneto-optical disc, the first contact portion contacting the cartridge holder when the cartridge holder is located at the loading position, the second contact portion contacting the disc cartridge when the cartridge holder is located at the loading position, the biasing magnet being positioned to face the magneto-optical disc through the opening formed on the disc cartridge at a predetermined distance spaced from a surface of the magneto-optical disc when the first contact portion contacts the cartridge holder and the second contact portion contacts the disc cartridge.
According to another aspect of the invention, there is provided a magneto-optical disc drive, which employs the biasing magnet positioning mechanism described above.
Since the position of the biasing magnet is defined by contact between the first and second contact portions and the cartridge holder and the disc cartridge, respectively, the biasing magnet can be positioned accurately at an operative position with a relatively simple structure.
Optionally, the cartridge holder is moved from the insertion/withdrawal position to the loading position through a horizontal path horizontally extending from the insertion/withdrawal position and a vertical path extending downward from an end of the horizontal path.
Further optionally, a spindle motor for rotating the magneto-optical disc may be provided on the chassis, a positioning of the disc cartridge in the vertical direction being achieved by the chassis, a positioning of the magneto-optical disc in the vertical direction being achieved by the spindle motor.
Further more, there is provided a magnet supporting arm provided on the chassis for rotatably supporting the biasing magnet, the magnet supporting arm being rockable about an axis which is parallel to a surface of the magneto-optical disc and is perpendicular to a radial direction of the magneto-optical disc in which the biasing magnet extends.
In this case, the biasing magnet described above may be supported by the magnet supporting arm such that the biasing magnet is rockable about an axis which is parallel with the rotational axis of the magnet supporting arm, at a substantially central portion of the biasing magnet in its extending direction.
Still optionally, the magnet supporting arm is provided with a first engaging portion, the cartridge holder is provided with a second engaging portion to engage with the first engaging portion, the rocking movement of the magnet supporting arm being performed when the second engaging portion moves vertically.
In particular, the second engaging portion biases the first engaging portion such that the magnet supporting arm is located at the predetermined position when the cartridge holder is located at the loading position.
Preferably, the second engaging portion is formed with elastic material.
Optionally, the disc cartridge includes a housing on which the opening is formed, a shutter being provided for closing the opening, the second contact portion contacting a part of the housing when the cartridge holder is located at the loading position.
Furthermore, the disc cartridge includes a housing on which the opening is formed, a shutter being provided for closing the opening, the second contact portion contacting a part of the shutter when the cartridge holder is located at the loading position.